Signal amplification system



July 9, 1957 H. M. SPENCER SIGNAL AMPLIFICATION SYSTEM 2 Sheets-Sheet 1Filed March 16, 1951 Henry M. Spe'ner INVENTOR.

2,798,903 Fatented July 9, 1957 SIGNAL AML'MFICATIUN SYSTEM Henry IV.Spencer, Norfolk, Va.

Application March 16, 1951, Serial No. 215347 Claims. (til. 179 471)This invention relates to amplification systems for electrical signalsor impulses of all kinds and it has for its main object to provide asimple and eflicient electronic amplification system with a highamplification factor which is free from those defects which usually areinseparable from such arrangements.

Amplification factors which are considerably above those obtainable bythe best electronic amplifier arrangements are usually obtained by meansof devices producing secondary electrons, the arrangement being suchthat the ratio of the number of electrons emitted by a cathode andimpinging on an electron liberating surface to the number of, secondaryelectrons which are released from said electron liberating surface ismuch larger than unity. In such a case the amplification which isobtainable in the amplifier system is of a magnitude which is a productof the amplification obtainable by the system without use of secondaryelectrons multiplied by a number corresponding to the said ratio.

However arrangements of this type have many inherent disadvantages suchas irregular amplification and lack of proportionality, as the secondaryelectrons repeatedly are drawn away from or deviate from the expectedcourse and special and complex control arrangements for the secondaryelectrons are therefore necessary. It is therefore an object of thepresent invention to provide an arrangement using secondary electronsand the multiplication of the amplifying effect produced by suchsecondary electrons without any special control, collecting or screening members.

According to the present invention the electrode of a signal amplifyingtube upon which a stream of accelerated primary electrons impinges andfrom which secondary electrons are emitted or released is not connectedwith any source of current. It forms with the control element of afurther electronic amplifier tube a completely insulated system. It isto be noted that also the control element is without further outerconnection so that the flow of secondary electrons is not onlycontrolled by the number of electrons intercepted by said controlelectrode but also determines the operating potential at which thecontrol electrode is maintained. The number of electrons intercepted bythe control element of the further electronic amplifier may thus alwaysbe equal or proportional to the number of secondary electrons emittedand ulti mately absorbed by an accelerating target electrode. In thisway a completely self-controlled arrangement results which automaticallytends to remain in and to return to a stabilized condition.

It is thus a principal object of the invention to provide a reliableamplification system with a high amplification factor which includes amultiplication factor obtained by means of secondary electrons producedin the system and corresponding to a high ratio of released secondaryelectrons to releasing primary electrons and which is of a simplifiedtype and can dispense with special means for the control of the saidsecondary electrons.

It is a further object of the invention to provide an 2 amplificationsystem of the above named type in which the multiplication issubstantially limited to the signal currents, while the no-signalcurrents are partly or practically excluded from such multiplication.

It is a further object of the invention to provide special electronictubes containing the amplification system which tubes may be providedwith a common cathode which is surrounded by suitable electron systemspermanently connected to obtain the above named results.

Further objects of the invention will be apparent from the followingdetailed specification.

The invention is illustrated in the accompanying draw-- ings showingseveral modifications or embodiments of the invention. It is however tobe understood that these embodiments of the invention are shown merelyby way of example and in order to explain the principle of the inventionand the best modes of applying said principle. The invention is onlyillustrated diagrammatically and the specification does not attempt todescribe all the possible modifications embodying the principle of theinvention. It will therefore be clear that a departure from the examplesillustrated in the drawings is not necessarily a departure from theprinciple of the invention.

In the drawings:

Figure l is a diagram of the connections illustrating a simplifiedembodiment of the invention.

Figure 2 is a perspective view illustrating diagrammatically anelectronic tube embodying the electrode system according to theinvention.

Figure 3 is a further diagram of the connections illustrating anotherembodiment of the invention.

Figure 4 is a perspective View illustrating diagrammatically anelectronic tube with those which have been shown in Figure 3.

Figure 5 is a diagram of a further modification of the invention.

electrode systems Figure 6 is a' perspective view illustratingdiagrammatically the electrode systems which have been shown in Figure 5when enclosed into a single tube.

Figure 7 is a diagram of a further modification of the invention,showing a series arrangement. l

The principle of the invention will be best understood when referring tothe simplified arrangement illustrated diagrammatically in Figure 1.This arrangement comprises an electronic tube with two grids 11, 12 theformer being an accelerator grid having the function of accel cratingthe electrons emitted by the cathode 14 and pass ing the control grid 12of the electronic tube.

The signal to be amplified and which may be of any character isreceived'at the terminals 3, 4 and is transmitted by means of an inputtransformer 13 to the control grid 12 and cathode 14 respectively.

The accelerator grid 11 is connected with the positive side of a hightension battery 2% by means of conductor 24 and the negative side of thebattery is connected with the cathode 14 by means or a suitable resistor19.

The plate 15 of the tube 10 is directly connected by means of conductor29 with the control grid 31 of second electronic tube 26 having acathode 25 connected with the negative side of the battery 20 by meansof a conductor 23 over the resist0r 19. The cathodes 14 and25 have thesame potential as will be seen from the diagram.

The plate 15 has no battery connection and may'con- T tain a materialfavoring the emission of secondary electrons or may be made of such amaterial or may be coated Which the apparatus or device for receivingthe amplified signals is'connected'.

The electrode systems of the tube or tubes and 26 cooperate in thefollowing manner.

Let it be assumed that electrons, the number of which is controlled bythe signal voltage arriving at the terminals 3 and 4 and transmitted tothe control grid 12, move towards and are accelerated by the highpositive voltage on the acceleratorgrid 11. These electrons will passthrough the grid and will impinge upon the plate 15. The plate in thiscase is not connected with any source of definite potential. Secondaryelectrons will be released from or will be knocked off the plate 15whenever an electron coming from the cathode and accelerated by the grid11 strikes the plate 15 and the number of secondary electrons thusreleased should be greater than the number of electrons impinging uponthe plate. All secondary electrons will be attracted to the acceleatorgrid 11 which has the highest positive potential and they therefore Willmove towards said grid. Thus the plate 15 constantly loses moreelectrons than it gains and for this reason it will become more and morepositive. As the plate 15, the conductor 29 and the control grid 31 oftube 26 forms a single insulated system which acts as an inter-systemcontrol, this system will become more positive when more electrons areaccelerated by the accelerator grid 11. The number of electrons movingtowards the accelerator grid depends on the number of electrons whichare permitted to pass the control grid 12 which, in its turn, isinfluenced by the magnitude of the signal voltage. It will thus be clearthat the voltage on plate will be multiple of the incoming signalvoltage and that the amplification factor will not only include theconventional amplification factors but Will also include amultiplication factor expressing the relation between the number ofaccelerated primary electrons and the number of released secondaryelectrons. The conventional amplification factor also includes theamplification obtained in the tube 26. As the ratio between primary andsecondary electrons may be high the gain obtainable with the arrangementas above described, will be correspondingly high and will be much higherthan the gain which is obtainable with conventional arrangements.

When the signalvoltage is lowered the number of primary electronsimpinging upon the plate element 15 is reduced and the number ofsecondary electrons released from plate 15 is reduced correspondingly.The plategrid systems 15, 31 therefore becomes increasingly negative andtherefore the output current in tube 26 also drops correspondingly. Itwill thus be clear that the plate current of tube 30 always varies withthe signal current.

The arrangement, as described, forms a coupling between the twoelectrode systems in the tubes 10 and 26 which so interlinks the saidelectrode systems that they act merely as the components parts of asingle system.

In order to maintain the described operation it is necessary that thenumber of electrons intercepted by grid 31 of tube 26 during operationmust always be such that the flow of secondary electrons from plate 15toward the accelerator grid 11 is maintained. It is also clear that itmay be of advantage to operate the system with a constant negativecharge of the electrode systems 1529--31, provided the dimensions of thetubes and spacing of the electrodes etc. permits operation with anegative grid bias on grid 31.

The above described system is therefore an amplification system withsecondary electron emission permitting to obtain an amplification factorwhich is much higher than that obtainable in systems operating with theelectrons emitted from the cathode, while at the same time the systemaccording to the invention preserves the character of a completelycontrolled and stable system.

In the diagram shown in Figure 1 two separate electronic tubes connectedin a suitable manner are illustrated which tubes may be suitablyselected from existing types. However, it may be of advantage toconstruct a special tube for the system which has been described aboveand in this case it is preferable to arrange the electrode systems,corresponding to those of the tubes 19 and 26 in the diagram, within oneand the same bulb and to use common electrodes wherever possible.

Figure 2 shows a special tube of this type. It comprises theconventional sealed and evacuated glass envelope 55. which is mounted ona base or socket 56. Within the evacuated bulb the cathode 33 isarranged which may be a common element of the electrode systems. Thecathode may be of the type heated by a special internal filament (notshown) the two ends of which are indicated at 34 and 35. The filament isconnected by means of wires 36, 37 with base pins 38, 39. The cathodecylinder itself is connected by means of wire 5th to the base pin 51.

In Figure 2 the upper electrode system corresponds to the systemindicated by the reference numerals 12, 11 and 15 in Figure 1. Itcomprises a control grid 40 and the accelerator grid 42 (correspondingto grid 11 in Figure 1) which grids are both shown in the formof aspiral.

The control grid 40 may be connected with an upper grid cap 44 arrangedon top of the evacuated glass bulb while the accelerator grid 42 isconnected by means of wire 48 with a base pin 49.

The two grids are surrounded by the cylindrical plate 45 (correspondingto plate 15 in Figure 1). All these, elements surround the upper portionof the cathode 33.

The second electrode system surrounds the lower portion of the cathodecylinder 33 in Figure 2 and it corresponds to the electrode system 31,30 in Figure 1. It comprises a grid 58 (corresponding to grid 31 inFigure 1) having theconventional spiral shape and the cylindrical anode60 (corresponding to anode 30 in Figure 1). The

grid 58 is directly connected with the plate 45 of the first: electrodesystem by means of wire 61 while the plate 60.

is connected with one "of the base pins 63.

The electronic tube illustrated in Figure 2 is thus a full equivalent tothe arrangement with two electronic discharge tubes.

In the arrangement shown in Figures 1 and 2 the amplification obtainedby means of electron multiplication.

due to the liberating of secondary electrons by impact is applied to thetotal current passing through the electrode systems'which includes theno-signal current as well as the signal current. It is however clearlyan advantage to amplify the signal currents by multiplication eitherwithout amplifying the no-signal current or by amplifying,

(Figure 3) the control grid 12 and an accelerator grid' 11 and-plate 15.The control grid is connected with the. secondary of the input or signaltransformer 18 whichis fed by thesignal currents at the terminals 3 and4. The accelerator grid 11 is connected with a high tension battery 20by means of conductor 24 and the plate 15 is connected with the controlgrid 31 of tube 26 as before described and forms with it an insulatedinter-system control while the plate 30 of the tube 26 is connected withthe high tension battery 20 over the secondary 28 of the outputtransformer.

In addition to the aforedescribed members and electrode systems,identical with those already described in connection with Figure 1, afurther set of electrodes 2],

17, 16 are added, one of said electrodes being a cathode 21 connectedwith the other cathodes 14- and'25 of the other electrode systems, whilethe electrode 16 is a grid which is connected with the plate-gridsystems 15-31.

The third electrode of the system. is. a plate 17. connected withconnection 24 leading to the high tension battery 20.

The plate voltage applied to plate 17 must be such that all theelectrons emitted by the cathode are attracted towards it so that theentire electron cloud surrounding the cathode is completely dissipated.The electrode system is thus operating at the saturation point. Thenumber of electrons attracted towards the plate is thus always the sameregardless of the voltage fluctuations which may occur by virtue of theconnection of the grid 16 with the conductor 29 of the plate-grid system15, 31. Likewise the number of electrons intercepted on the grid 16 willalways be the same or nearly the same and this number is preferably madeequal to the number of secondary electrons which were attracted towardsthe accelerator grid 11 and which corresponds to the electron flowmaking up the no-signal current component. Therefore the remainder ofthe system which works approximately. in the manner which has alreadybeen de scribed in connection with Figure 1 uses the multiplication bymeans of secondary electrons solely for the purpose of multiplying thesignal current plus a fraction of the no-signal current which may bemade as small as practicable. The voltage of the three electrodes 11, i6and 31 is always equal and it is determined by the control grid 12 ofthe first electronic tube 10 which controls the current flowing throughthis tube towards the plate 15.

The three electrode systems may again be enclosed within and form partof a single electronic tube shown diagrammatically in Figure 4. Theparts corresponding to those already described in connection with Figure3 are designated by the same reference numerals and their operationtherefore need not be described.

The multiple electronic tube illustrated in Figure 4 comprises theevacuated bulb or envelope 55 carried by a socket 56 which is. providedwith a number of base pins and with a grid cap 44 on the top of the bulbconnected with a sealed in connection in the top of the bulb.

The electrode system consists of the cathode 33 which forms the commonelement of all electrode systems and which is heated by a heaterfilament (not shown) the ends 34, 35 of which project from the cathodecvlinder and are connected with base pins 38, 39 by means of the sealedin wires 36, 37. The cathode cylinder itself is connected with a basepin 51 by a sealed in wire 50.

The cathode is surrounded by a first electrode system which consists ofthe control grid 40, connected with the grid cap 44 at the top of thebulb 55, of an accelerator grid 42 and of a plate 45. The secondelectrode system (the lowermost system in Figure 4) consists of grid 5%and plate 60 the latter being connected by means of a sealed in wirewith base pin 63.

Between the two above described systems a third electrode system isarranged which surrounds the common cathode 33 and which consists ofgrid 65 which has the shape of a spiral wire and which may be directlyjoined at 68 to grid 58 of the lower system on one side and to plate 45of the upper system at 69 on the other side. A plate 66 is connectedwith the accelerator grid wire 48 leading to base pin 49 and is furtherconnected with the accelerator grid 42 of the upper system by means of ashort connection wire '71.

A simplified arrangement of the type illustrated in Figure 3 is showndiagrammatically in Figures 5 and 6. The reference numerals which areidentical with those used in Figures 3 and 4 indicate parts which arethe exact equivalents to those already described.

The diagrams in Figures 5 and 6 differ from those above described mainlyby the fact that the third electrode system consists merely of acollector electrode in the shape of a plate or a ring 70 (Figure 5)indicated at 75 in Figure 6. In Figure 5 the collector electrode isshown as a plate facing the cathode 21 in a separate evacuated bulb inthe manner of a diode and, in fact, a diode of an existing type may beused for this purpose. In Figure 6 the collector electrode is shown as aring 75 arranged between the two electrode systems 40, 42, 45 and 58,60. The collector ring is in this case connected with the conductor 29of the plate-grid system 15, 31 (Figure 5) and in the arrangement shownin Figure 6 the ring 75 is joined to the electrodes 45 and 58 by shortconnecting pieces 76, 77. The collector electrode is therefore notdirectly joined to a positive potential, but is joined to a system whichin order to make it operative, must always be positive to a desiredextent. This arrangement is therefore dependent on suitable dimensionsand current and voltage values.

Essentially however the operation is the same as that already describedin connection with Figures 3 and 4. The collector ring '75 must becharged with a positive potential which is capable of drawing towards itall the electrons emitted by the cathode 21 whatever the fluctuation ofthe said potential so that the electron cloud is completely dissipatedand the saturation point is reached. Regardless of such fluctuations thenumber of electrons drawn towards the collecting electrode issubstantially constant and does not vary with the signal fluctuations.The number of electrons collected on the electrode must be equal to thenumber of secondary electrons in the current flow between electrodes 15and 11 (42 and 45 in Figure 6) corresponding to the constant nosignalcurrent. The remainder of the system operates substantially as anelectron multiplier system for the signal currents, as only a smallfraction. of the Ito-signal current is amplified by these means. Thedimensions of the collector electrode or ring must of course be chosencorrespondingly and they are preferably so selected that the collector'70 very nearly but not fully supplies the plate 15 with electrons inreplacement for those which have been knocked out by the impact of theprimary electron stream. The electrodes 15, and 30 will then, besulficiently positive to make the grid 31 intercept the number ofelectrons which corresponds to the diiierence.

It will be seen from the above description that the system described isa very eificient amplification system with a high amplification factorwhich is finely adjustable. The system is free of all thoseirregularities which in most electron multiplying arrangements areinseparable from such devices and which cause a non-linear response andnon-uniform amplification and a distortion of the output unless specialmeans are provided to suppress these effects. The system as describedmay use suitable tubes such as existing and as marketed. The tubes mayhave any number of grid electrodes when a suflicient number of types ofmulti-grid tubes is available to select suitable tubes for the purposesof this invention from them. The additional grids arranged in theelectrode systems between the control grid and the acceleration grid maybe used in any well known manner as the present invention does in no wayaffect their operation. The same may be said of grids inserted betweenthe control grid of the second tube and the plate. The electrode systemof the last tube may of course also be that of a beam power tube.

It will also be understood tht the system according to this invention,for instance the system illustrated in Figures 1 and 2 may consist ofmore than two electrode systems with several tetrodes, such as tube 1%),arranged in series (Figures 7). The plate 15 of the first electrodesystem of the series is in this case connected with the control grid 41of a further tetrode Sit, the plate 47 of which may again be connectedwith the control grid of the next tetrode if the series should consistof more than two tetrodes. The plate of the last tetrode (47 in Figure7) is then connected with the control grid 31 of the electrode system25, 31, 36 which is connected with the output transformer. Theaccelerator grids d3 of the ad ditional tetrodes of the series are allconnected with condoctor 29 leading to the positive side of the battery.The

electrode system 25,'31,'30 is shown as a triode, but may have anynumber of grids connected in the conventional manner. In addition asshown in 'Figure7, electrode systems 21, 16, 17 similar to thosedescribed in connection with Figure 3 or electrode systems 21, 70 suchas shown in Figure 5 may be inserted.

Further it will be understood that unessential details may be changedwithout departing from the essence of the invention as defined in theannexed claims.

"Having described the invention, What is claimed as new is:

-l. An electronic amplifying system, comprising a plurality of electrodesystems, each having a source of primary electrons forming the cathode,a source of current for providing the no-signal current of the system, afirst one of the systems being a tetrode system including a controlgrid, connected with a signal input circuit, a combined electronaccelerating target electrode connected with a source of positivevoltage of the said source of current, and a plate adapted to emitsecondary electrons upon impact of primary electrons on the same whichhave been accelerated by the accelerating and target electrode, thesurface of the secondary electron emitting plate and the acceleratingand target electrode facing each other di-- rectly. a diode system and atriode system, the latter ineluding a control grid, and the diode systemincluding a collector electrode facing the cathode of the diode system,the control grid of the triode system and the collector electrode beingboth directly and exclusively connected with the plate emittingsecondary electrons and forming with the said plate an otherwiseinsulated system, the diode system being dimensioned to produceoperation at the saturation point with the positive voltage imparted toit, an anode in the triode system connected with a positive voltagefurnished by the source of currents, the positive voltage being soadjusted that the number of electrons intercepted at the control grid ofthe triode system corresponds to the number of secondary electronsemitted by the plate of the tetrode system which are due to the nosignalcurrent, an output circuit connected to the anode of the triode sysem,the amplification of the signal current in the output circuit being thusproportional to the product of the tube amplification factor and theratio of primary and secondary electrons, while the nosignal currentamplification is constant and is equal to a predetermined fraction ofthe no-signal current.

2. An electronic amplifying device comprising a plurality of coaxiallyaligned cylindrical electrode systems. arranged in one common evacuatedenvelope, all systems having a common central cathode emitting primaryelectrons, a first one of said systems includinga control gridsurrounding the cathode, an independent outer cylindrical plateelectrode, the inner surface of which directly faces and surrounds acombined electron accelerating and target forming grid electrode whichsurrounds the said control grid and cathode and is unconnected with theplate which surrounds it, said plate electrode being adapted to emitsecondary electrons upon impact of primary electrons; a second one ofsaid coaxially located aligned elec trode systems including a secondcontrol grid surrounding the cathode, directly connected with the plateelectrode of the first system and forming with said plate electrode aninsulated otherwise unconnected system forming an inter-system control,an anode surrounding the control grid of the said second one of theelectrode systems, terminal connections for the anode, for the cathode,for the control grid and for the accelerator and target electrode of thefirst one of the electrode systems, and a further electrode systemsurrounding the cathode consisting of a collector ring, said collectorring being connected with the insulated otherwise unconnectedplate-control grid system forming an inter-system control and beinginserted between said first one and'the second one of the electrodesystems. I

3. An amplification system for signal currents comprising a source ofcurrents, a plurality of electronic discharge .tube electrode systemseach containing a cathode forming a source of primary electrons, thecathodes of. all electrode systems being connected to a common referencesystem; the first one of said-electron systems including in addition acontrol electrode, means to impose a signal on said control electrode,an accelerating electrode for the primary electrons emitted by thecathode, said accelerating electrode being connected with a. positivevoltage supplied by the source of current, and a plate electrode adaptedto emit secondary electrons upon bombardment with theprimary electrons,which plate electrode faces said accelerating electrode and isunconnected with any other electrode of its system; a second one'of saidelectrode systems including an anode connected with the positive side ofthe source ofcurrent and also with an output circuit and furtherincluding a control grid which is connected with the plate electrode ofthe first one ofthe electrode systems and forms with it an insulatedinter-system control, the primary electrons emitted by the cathode ofthe first one of the electrode systems and impinging upon the plateelectrode of the first one of said systems, producing secondaryelectrons attracted to the accelerated electrode as the targetelectrode, the change of voltage due to the signal producing afluctuation of the primary electrons and a corresponding fluctuation ofthe emission of secondary electrons on the plate electrode entailing achange of voltage in the inter-system control controlling the outputcircuit of the second one of the electrode systems; a third one of saidelectrode systems including an electrode connected with the aforesaidinter-system control, the last named electrode of the third electrodesystem being dimensioned relatively to another electrode of the samesystem for operation on the saturation point attracting permanently allthe electrons produced within said third electrode system, said firstsystem thus providing the inter-system control with a number ofelectrons which is in a predetermined relation to the number of primaryelectrons producing a no-signal current in the first electrodesystem.

4. An amplification system for signal currents comprising a source ofcurrents, a plurality of electronic discharge tube electrode systemseach containing a cathode forming a'source of primary electrons, thecathodes of all electrode systems being connected to a common referencesystem; the first one of said electron systems including in addition acontrol electrode, means to impose a signal on said control electrode,an accelerating electrode for the primary electrons emitted by thecathode,-said accelerating electrode being connected with apositive'voltage supplied by the source of current, and a plateelectrode adapted to emit secondary electrons upon bombardment with theprimary electrons, which plate electrode faces said acceleratingelectrode and is unconnected with any other electrode of its system; asecond one of said electrode systems including an anode connected withthe positive side of the source of current and also with an outputcircuit and further including a control grid which is connected with'theplate electrode of the first one of the electrode systems and forms withit an insulated inter-system control, the primary electrons emitted bythe cathode of the first one of the electrode systems and impinging uponthe plate electrode of the first one of said systems, producingsecondary electrons attracted to the accelerated electrode as the targetelectrode, the change of voltage due to the signal producing afluctuation of the primary electrons and a corresponding fluctuation ofthe emission of secondary electrons on the plate electrode entailing achange of voltage in the inter-system control controlling the outputcircuit of the second one of the electrode systems; a third one of theelectrode systems including a control electrode and an anode, the latterconnected with the positive side of the source of current, while thelast named control electrode is connected with the inter-system controlconnecting the plate of the first one of the electrode systems and thecontrol grid of the second one of the electrode systems, said anode ofthe third one of the electrode systems and the control electrode of thesame system being dimensioned and the voltage supplied to the anodebeing selected to produce operation of the third electrode system at thesaturation point, said anode of the third electrode system attractingpermanently all the electrons produced in said third electrode system,the latter thus providing the inter-system control with a number ofelectrons which is in a predetermined relation to the number of primaryelectrons producing a no-signal current in the first system.

5. An amplification system as claimed in claim 4 wherein the third oneof the electrode systems consists of a diode.

References Cited in the file of this patent UNITED STATES PATENTS Jonkeretal Jan. 31, 1939 Jonker et al. Feb. 7, 1939 Rinia Dec. 24, 1940Eaglesfield Dec. 31, 1940 Skellett Sept. 21, 1943 Strutt et al. Jan; 13,1948 Van Weel Feb. 14, 1950 Atherton May 22, 1951 FOREIGN PATENTS FranceAug. 9, 1937 France Apr. 11, 1939 Australia Dec. 6, 1939

